For the most part, our laboratory has evaluated the effect of hemodilution and hemodynamic manipulation, and nitric oxide manipulation on cerebral ischemia. We accomplish our studies using three different models of cerebral ischemia in the rat. The first model is an open craniotomy model in which the middle cerebral artery is tied off for 120- minutes and allowed to reperfuse for 180-minutes. By in large we have replaced this model with a less invasive model in which a suture is passed (intraluminally) into the middel cerebral artery via the external carotid artery. A final model of cerebral ischemia which we employ evaluates vasospastic cerebral ischemia. In this model a subarachnoid hemorrhage is induced and areas of cerebral ischemia are assessed. During the past year we have assessed the effect of a molecular hemoglobin solution of cerebral ischemia in models of middle cerebral artery occlusion and subarachnoid hemorrahage. We have used the Drexel system to derermine cerebral blood flow, areas of low cerebral blood flow ( ischemia); and we have determined the cerebral infarct volume utilizing the above system.